Printing presses, including offset lithographic web printing presses, often utilize printing plates placed on a plate cylinder of a press to provide an image carrier. Ink is then applied to the image carrier so that the image eventually is transferred to a web or sheet of material, such as paper.
An offset lithographic web printing press typically includes a plate cylinder, a blanket cylinder and an impression cylinder supported for rotation in the press. A single printing plate having a surface defining an image is secured to the plate cylinder. Ink is applied to the image-carrying surface of the printing plate. A printing blanket having a transfer surface lies on the blanket cylinder. The printing blanket surface contacts the printing plate at a nip between the plate cylinder and the blanket cylinder. The printing plate surface transfers the image to the printing blanket surface at the nip and the printing blanket surface then transfers the image to a web of material, such as paper.
The printing plate typically is a flat rectangular sheet of material and is mounted on a plate cylinder by wrapping the plate around the plate cylinder and inserting the ends of the plate into an axially-extending gap in the plate cylinder. However, the gap in the plate cylinder between the ends of the plate can create undesirable vibrations and an undesired non-printing area.
Other offset printing presses use tubular and continuous printing forms to eliminate the gap on the plate cylinder. These presses however require complicated axial removability through the frame and a complicated construction for securing the tubular printing form on the plate cylinder, such as an air cushion release system.